1. The Field of the Invention
The present invention relates to methods and systems for controlling and monitoring pressurization data. More specifically, the methods and systems may be used to control and monitor the pressurization of a control syringe during certain medical procedures.
2. The Prior State of the Art
One of the most common medical procedures that requires precise measurement of pressurization data is balloon coronary angioplasty, more technically known as percutaneous transluminal coronary angioplasty (xe2x80x9cPTCAxe2x80x9d). PTCA was developed about twenty years ago as an alternative to existing techniques for treating coronary artery disease. Bypass surgery and drug therapy had been the principal treatment options of the day. However, bypass surgery is extremely traumatic on the patient and drug therapy attempts only to compensate for the effects of coronary artery disease as opposed to treating the disease itself. PTCA, in contrast, is a comparatively minor procedure directed at eliminating (rather than merely compensating for) the dangers posed by coronary artery disease. Notwithstanding the comparatively minor nature of PTCA procedures, strict control and monitoring of pressurization data is essential to the patient""s safety.
A leading cause of death for many years, coronary artery disease is a narrowing or blockage (xe2x80x9cstenosisxe2x80x9d) of the arteries that supply oxygen-rich blood to the heart. In coronary artery disease, the narrowing or blockage is caused by artherosclerosis, a buildup of waxy material (cholesterol and other fats) called plaque inside the artery walls. The waxy buildup reduces the amount of oxygenated blood that can flow to the heart through the coronary arteries. For many, this reduced blood supply results in a symptom of coronary artery disease called angina pectoris (xe2x80x9canginaxe2x80x9d).
Angina is characterized by chest pain or pressure that may radiate to the arm or jaw, and is caused by insufficient oxygen being delivered to the heart muscle. At rest, the reduced flow of oxygenated blood caused by coronary artery disease may remain undetected, particularly in the early stages of the disease. However, under exertion or stress, the heart demands increasing amounts of oxygen to continue functioning properly. When the narrowed or obstructed coronary arteries prevent the heart from receiving the extra supply of oxygen-rich blood that is required to sustain a given heart rate, the resulting oxygen deficiency causes angina.
As noted earlier, up until the early seventies there were two basic ways to treat coronary artery blockages: drug therapy or coronary artery bypass surgery. Drug therapy involved administering various medications to decrease the work of the heart by slowing the heart rate, dilating the blood vessels, or lowering blood pressure. However, drug-based treatment did not restore normal supply of blood to the heart, the medicine simply alleviated the discomfort that may be associated with coronary artery disease. The underlying problem of reduced blood flow remained and continued to present a risk that at some point the blockage would become serious enough to require surgical intervention.
In coronary artery bypass surgery, a blood vessel from the chest or leg is grafted beyond the point of blockage so that blood flow detours around the blockage in order to reach the heart muscle. In some severe cases, multiple bypasses must be performed. As is well known, coronary artery bypass surgery is an expensive, high-risk procedure and often requires prolonged hospitalization and recovery periods.
PTCA, in contrast, is a much less traumatic procedure than coronary artery bypass surgery. PTCA procedures typically last about two hours and are performed under local anesthesia. Often, a patient can be walking and active in a matter of hours. Because PTCA is much less expensive and less traumatic than bypass surgery and yet in many cases effectively removes blockage, PTCA has experienced a dramatic increase in the number of procedures performed each year. For example, according to some reports, by 1987 some 200,000 patients suffering from coronary artery disease had been treated using PTCA. Significantly, as of 1987, approximately six million cases of coronary artery disease were reported in the United States alone. Therefore, PTCA may be expected to continue playing an important role in the treatment of coronary artery disease.
In performing PTCA, an introducer sheath is inserted through an incision made in the groin or in the artery of an arm. Through a catheter that is introduced through the sheath, an x-ray sensitive dye is injected into the coronary artery. The dye enables the doctor, through the use of real time x-ray techniques, to clearly view the arteries on a television monitor and to thereby locate the artery blockage. With the help of images from the x-ray monitor, a balloon-tipped catheter is fed over a guide wire and advanced through the artery to the point of the blockage.
The balloon catheter is advanced to the middle of the blockage site. This catheter, which is also filled with a radio-opaque fluid, is coupled at its other end to a control syringe being manipulated by a cardiologist. Once the balloon catheter is in place, the cardiologist uses the control syringe to inflate the balloon for time periods ranging from about 20 to 60 seconds. At the end of each time period, the cardiologist operates the control syringe to deflate the balloon. Typically, the inflation/deflation cycle is repeated several times to compress the plaque on the arterial wall. After the results are checked, the balloon catheter and guide wire are removed.
Even though PTCA is a much less traumatic procedure than coronary artery bypass surgery, exacting control with respect to inflation pressure and duration of the inflation periods is essential to the safety of the patient. When the balloon catheter is inflated so as to begin compressing the plaque, blood flow to that area of the heart is temporarily shut off. Depriving the heart muscle of its blood supply, even temporarily, creates the potential for initiating cardiac arrest. Accordingly, the attending cardiologist and other personnel must carefully control both the pressure exerted on the artery walls and the duration of the temporary blockage. The inflation pressure and duration for each inflation are based on the cardiologist""s assessment of the patient""s overall health and ability to withstand a temporary stoppage of blood flow to the heart.
In the past, PTCA syringe systems have used standard pressure gauges to sense and read the pressure of an inflated balloon catheter, with human observation of stop clocks and the like controlling the duration of each inflation. While these prior art techniques have been widely used with success, they introduce a serious risk of human error. The gauges used on such syringe systems are often awkward and difficult to read accurately, and are subject to malfunction. Thus, improper recording of inflation pressure and/or duration may occur.
To enhance the monitoring, display, and recording of pressurization data, U.S. Pat. No. 5,300,027 issued to Foote, et al. on Apr. 5, 1994 and entitled xe2x80x9cSYSTEM AND METHOD FOR MONITORING AND DISPLAYING BALLOON CATHETER INFLATION AND DEFLATION DATAxe2x80x9d (hereinafter xe2x80x9cFootexe2x80x9d), which is incorporated herein by reference, introduces an electronic control system. The control system includes a monochromatic LED display showing the pressurization data (number, time, and pressure) for the current pressurization cycle.
At the time, Foote represented a vast improvement over the prior art. Nevertheless, continuously improving medical care requires constant innovation. In the case of monitoring and controlling pressurization data, there is an ongoing need to enhance the information that may be conveyed to a cardiologist and/or clinician. The systems and methods of the present invention offer novel solutions to providing medical professions with immediate access to information, helping insure the best possible healthcare for their patients.
The present invention is directed toward methods and systems for electronically tracking pressurization data. For example, the present invention includes an electronic controller for receiving, displaying, and storing pressurization data. The present invention combines novel control features and display elements for conveying pressurization data in ways that were previously unknown. A preferred embodiment of the present invention is designed for use in displaying, monitoring, and storing pressurization data during a balloon coronary angioplasty procedure for treating coronary artery disease. Throughout these balloon catheter procedures, it is imperative for the medical professional performing the surgery to have immediate access to clear and accurate pressurization data.
In this environment, the electronic controller receives pressurization data from a control syringe equipped with a transducer for converting pressure information to electrical signals that can be interpreted by the controller. Optionally, the electronic controller may be attached to a printer and may also act as host for a remote electronic controller. When connected to a remote electronic controller, the host functions and displays are duplicated in both controllers. However, a control syringe may be connected only to the host.
As described above, balloon catheter procedures for treating coronary artery disease involve the insertion of an inflatable balloon catheter into a narrowed or blocked area of the arteries supplying oxygenated blood to the heart muscle. Using a control syringe, a clinician treating coronary artery disease inflates the balloon to compress plaque that has been deposited within the artery walls and is restricting the flow of blood. Because the inflated balloon temporarily stops blood from flowing through the artery, it is vital for the physician to know how much pressure the balloon is exerting on the artery wall and how long the balloon has been inflated.
The principal danger of the procedure is that interrupting the flow of blood to the heart will cause the patient to experience a cardiac arrest. Therefore, the precise pressure and duration of each inflation must be based on an assessment of the patient""s health and the patient""s ability to withstand temporarily halting the flow of blood to an area of the heart. Because the consequences of over inflating or stopping blood flow for too long are grave, the capability to clearly and accurately track pressurization data is critical to appropriate patient care.
The present invention is an advancement over the prior art in its ability to convey pressurization data unambiguously. Specifically, the present invention provides a unique combination of visual cues and control features to insure accurate analysis of pressurization data. For example, the background color of the display area changes when pressurization data transitions from one pressurization state to another (e.g., from a state of depressurization to a state of pressurization). Each transition between pressurization states also starts a timer showing the elapsed time since the transition occurred. To insure a clear understanding of pressurization data, units of measure are included with the display of pressurization values.
Together with changes in background color, a pressurization arrow in the display area visually communicates whether pressurization values indicate a state of pressurization or a state of depressurization. Within the pressurization arrow, the electronic controller displays a count of the pressurization cycles (i.e., the number of times pressurization values have transitioned between a predefined sequence of pressurization states). The bottom of the display area includes software buttons that allow for altering the operation of the electronic controller, such as how the display is organized. Specifically, one of the software buttons toggles between a text display mode and a graphical display mode.
The display also includes a touch interface for all interaction with the electronic controller. Pressing the display area showing the units of measure toggles between the various options for pressure units. Likewise, the software buttons along the bottom of the display are also activated through the touch interface.
To insure accurate pressure measurements, the present invention may include at least one reference standard. The reference standard may be read at various times during operation of the electronic controller to verify that the controller measures the same pressure at a consistent value. Minor variations in reference standard measurements are accounted for by defining an appropriate tolerance value or range.
Notwithstanding that the foregoing summary and later detailed description refer to balloon catheter treatment of coronary artery disease, the present invention is in no way limited to use in those procedures or even limited to medical applications in general. The present invention integrates various display cues, setup parameters, and control features to provide novel methods and systems for tracking pressurization data. These methods and systems may improve healthcare or offer the benefits of clarity, accuracy, and convenience to any other field or application.
These and other objects, features, and advantages of the present invention will become more fully apparent from the following description and appended claims, or may be learned by practicing the invention as set forth below.